Automatic alarm selector



y 1951 F. s. HOLLOWAY 2,552,174

AUTOMATIC ALARM SELECTOR Filed Feb. 14, 1948 (MM/ABLE) INVENTOR FREDERICS. HOLLOWAY BY ATTO EY Patented May 8, 1951 AUTOMATIC ALARM SELECTORFrederick Sydney Holloway, Sydney, New South Wales, Australia,

assignor to Amalgamated Wireless (Australasia) Limited, Sydney, NewSouth Wales, Australia, a company of New South Wales, Australia IApplication February 14, 1948, Serial No. 8,363

' In Australia December 5, 1946 Section 1, Public Law 690, August 8,1946 Patent expires December 5, 1966 6 Claims, 1 This invention relatesto an improved automatic alarm selector arrangement for giving an'alarmon the receipt of a predetermined wirelesssignal (such as is used forrequesting aid'by ships at sea) composed of a regular series of dashesof definite length and spacing.

sent by hand, and the timing done by the'aid of a watch, it is'essentialfor the effective operation of any automatic alarm system that sometolerance be permitted in the length of the dashes and 7 spaces, so asto allow for errors in sending. The embodiment of the inventionto bedescribed is, therefore, designed to respond to signals consisting ofdashes of from between three and one-half to four and one-half secondsduration, separated by spaces of less than one and one-half seconds.This lattitude allows for an error of plus or minus one-half second inthe length of each dash, a tolerance which, it has been found inpractice, is sufiicient for hand operating.

Various known automatic signal operated alarm systems have been based onthe use of mechanically driven cams with clutch mechanism arranged to bedriven at constant speed by motors, though other systems utilizingdashpot relays consisting of small pistons working in suitable cylindersfor securing timing have been used. Such known mechanical arrangements,however, suffer from the disadvantages of being difficult and expensiveto build, and when constructed difiicult to maintain in adjustment.

It has been found that the wear and tear on mechanical alarm systemsreduces the life of the parts to a considerable extent.

Otherautomatic signal operated alarm systems employ thermionic valves incircuit arrangements designed to overcome the disadvantages associatedwith the known mechanical systems. Arrangements of this type provide aselector system which has its timing based on electrostatic controlrather than on a mechanical circuit scheme. Time constantresistance-reactance circuits function to time the operation of varioussensitive relay devices through themedium of thermionic valves.

Although'thejknown, thermionic valve types of selector overcome to alarge, extent the disadvantagesassociate'd with the mechanical schemes,

they are not entirely satisfactory as they depend for their successfuloperation on the stability of a number of factors which are noteconomically controllable. For example, variation in the tension of therelay springs, fluctuation of. the operating potentials applied toelectrodes of the valves, or agingof the valves themselves, willcauseunreliable operation of the system..

In the past therefore it has been the practice in thermionic systems ofthe foregoing nature to employ wherever possible suitable controldevices in order to stabilize the variable factors. Such controldevices, apart from the fact that they are expensive .to construct,introduce undesirable complications into the circuit arrangement andconstructionof the apparatus.

'The object of the present invention is to provide an improved automaticalarm selector in which the disadvantages associated with knownmechanical or thermionic valve systems are avoided.

A further object of this invention is to provide an improved automaticalarmselector which employs no moving parts other than electric relays,which is independent-within wide limits of potential supply variation,and which utilizes in expensive relays.

A still further object of this invention is to provide an improvedautomatic alarm selector which is reliable in operation as well as beingsimple and economical to construct.

The above objects are achieved in accordance with the present inventionby providing, in-automatic selectors of the electronic type, meanswhereby the energizing current of individual selector relays in thesystem is caused to vary substantially instantaneously from zero to therequired operating value when the particular energizing circuit iscompleted.

More specifically an improved automatic alarm selector in accordancewith the present invention comprises in combination a signal relayresponsive to incoming signals, a first selector relay the operatingwinding of which is energized by the dischargecurrent of a gridcontrolled gas discharge device, circuit means including a time constantnetwork for applying control potentials to the grid of said device apredetermined time after the operation of said signal relay, a storagecircuit for accumulating potential increasing with successive operationsof said first selector relay, an alarm or indicating device, meansresponsive to potentials of a predetermined value in said storagecircuit for actuating said alarm or indicating device; a second selectorrelay which functions to discharge said storage circuit when theoperating winding of said second selector relay isene'rgized by thedischarge current of a second grid controlled gas discharge device,circuit means including a time constant network for applying controlpotentials to the grid of said second discharge device when said firstselector relay has been operated for a predetermined time; and athird;selector relay the op erating winding of which is energized by thedischarge current of a third grid controlled gas discharge device todischarge said storage circuit a predetermined time after the opening ofsaid first selector relay. a

For a more complete understanding of the invention and the manner inwhich it is to be carried out, attention is now directed to thefollowing description in connection with they accompanying drawing whichillustrates one method of carrying out the invention. a t In order tosimplify the description, only that portion of an automatic alarm systemwhich is necessary for an understanding of the invention is indicated inthe drawing.

The automatic alarm selector diagrammatically illustrated comprisesessentially a signal r'elay I, the operating winding I I of whichisenergized in any convenient manner from the output circuit ofconventional radio receiving apparatus (not shown). 7

Associatedwith the signal relay I are a plurality of relays 2, 3 and 4which are individually associated with operating gas discharge devices'5, flande, respectively. Any convenient type of grid controlled gasdischarge device, such as a triode or tetrode, may beused withoutaffecting theoper'ation of the invention. I Bielays Z 3 and 4 areadapted to control. potentials built up in the storage device G1, whichpotentials serve to actuate an alarm or indicating device (notshownlthrough the gas discharge device I and the relay 5 in the mannerherein after tobe described;

Operati g potentials are applied to the anodes of the'clevic'e's T, 8, 9and I 0 through the operating windings I2, I3, I4 and I5 of theassociated relays 2, 3, 4and 5, respectively, from thepositive terminalI 5 of any convenient potential supply source (not shown). of thepotential supply source is connected to a point of zero potential, suchas the earth I 8.

The control potential at which the devices I, I3, Sand I0 are renderedconductive is controlled in the present example by the applicaticnofsuitable positive biasingpotentials to the respective cathodes I9, 20,2|, 22 of the devices I, 8,

The desired biasing potentials for the cathodes I9, 20, 2|. and 2201?the devices 1, a, a and It may be derived from any convenient sourcesuch as, e. g., the potential divider network 23 connected across theterminals I6 and I8 of the potential supply source (not shown).

In the operation of the system, signals detected and amplified in theusual radio receiver (not shown) cause the relay I to be operatedimmediately upon receipt of a signal.

v Whenrelay I operates, it removes the connection between the controlgrid of device 1 and ground (contacts 24) and allows condenser CI todischarge through RI raising the. potential on said control grid,previously negativev with respect to cathode. It also closes thecontacts 25 which complete a circuit for the application of The negativeterminal I! 4 operating potentials to the anodes A of the devices 1, B.V

The discharging rate for the condenser CI is adjusted by suitable choiceof the resistance RI, the value of the latter being such that at the endof three and one-half seconds of continuous discharging the positivepotential on the condenser CI causes the gas discharge device I to fire,and the relay 2, which is energized by the discharge current, isoperated. As the discharge current through the device 1 increases fromzero to its maximum value practically instantaneously, full operatingcurrent flows through the energizing winding I2 of the relay 2 causingit to operate immediately the de- Vice 1 is caused to fire.

Relay 2, when operated, closes contacts 26, 21 and opens contacts 28,29. The closure of contacts 2? completes a circuit whereby the storagecondenser. C'I is charged through the condenser C3 to a certainpredetermined value. Each successive operation of the relay 2 willincrease the potential stored in C1 by approximately equal amounts, to avalue such as will cause the device II] to ignite.

As the discharge current of device In is caused to flow through theenergizing winding I5 of the relay 5, the ignition ofthe device I0 willcause operation of the relay 5 thereby completing the energizing circuitof an alarm bell or bells or other indicating device through closure ofthe contacts 30.

The variable bias potential applied to the cathode 22 of the device I0facilitates a selection of the control potentials required to causeignition. By suitable adjustment of the cathode biasing potential thedevice I0 maybe caused to re at. a control potential equal to that builtup on the storage condenser C1 by the requisite number of operations ofthe relay 2. v The operation of the relay 2 disconnects the control gridof device 3 from ground, and allows condenser C5 to discharge throughresistorv R2 raising the potential on said control grid. The valuesofthecondenserC5 and the resistor R2 are such that alter a period of onesecond the potential appliedto the grid from the condenser C5 will'cause the device, 8 to ignite. The relay, 3 which is energized by thedischarge current of the device 8 is immediately operated to close thecontacts 3|, thus providing a short circuit path to remove any chargeaccumulated on the storage condenser CI.

From the foregoing it will be seen that if an incoming signal lasts formore than 4.5 seconds (3.5+1) after the operation of relay I, relay 3will be operated to reject such signal by discharging the storagecondenser 01. Only signals whose length is between 3.5 and 4.5 will beaccepted and allowed to build up potential on the storage 'condenserC'I.

In order to ensure that only signals which are separated by the correctspacing intervals are accepted by the apparatus, a further selectorrelay 5 and associated gas discharge device 9 is provided.

, If at any time the incoming signal ceases, relay I will bede-energized and return to its normal condition, thereby opening thecontacts 25, and closing contacts 24.

The closing of contacts 24 restores the initial negative bias on deviceI, while the opening of the contacts 25 open-circuits the anodepotential supply circuit of the devices I and 8. The removal of anodepotential from the devices 'I and 8 5 extinguishes thedischarge in thedevice I, thereby allowing the relay! to return to its normal conditionand also prevents ignition of the'device Band consequent operation oftherelay 3. 1 N In thenormal (no-signal) condition of relay 2 the contacts2%, '2"! are opened and thecontacts 28, 29 and 39 are closed.

In this condition of the relay 2, operating potentials are applied-tothe anodeof the device-9 through the contacts-2i], while opening ofcontacts 26 removes earth connection from grid of device 9 and allowssaid grid to charge positively due to discharge of C6 via R3.

The discharging rate of the condenser 06' is governed by the value ofthe network components. I

The value selected for these components in the present example "is suchthat at the "end of five seconds the positive potential applied to "thegrid from the condenser C6 is suflicient to cause ignition of the device9. i The relay 4 is immediately operated by" the discharge'current ofthe device 9 flowing through its energizing winding l4. Resultantclosure ofth'e contacts32 functions to discharge the storagecondenser'Cl, thereby restoring the apparatus to the waiting condition.

Thus, if a space orrnore than ;1.5 seconds exists between two successiveoperations of the relay 2, the-total interval (for a 3.5 second dash)between two openings" of the relay 2 is more than five secondsandisnotacoeptable to the apparatus. To put it another way, if the timeinterval which elapses between'two successive operations of the relay 1is in'excess of five seconds, made up of 3.5 seconds for the "signal and1.5 for the space, the apparatus is restored to the waiting is appliedto the storage condenser Cl. Further signals of the correct length andspacing will result in a repetition of the above operation and raise thepotential on the storage condenser C! in steps to a value which willcause the device Ill to ignite with a consequent actuation of the alarmbell or bells or other indicating device through the operation of therelay 5.

The number of successive operations of the relay 2 which are required toset off the alarm is determined by the positive biasing potentialapplied to tthe cathode 22 of the device Ill.

The bias is usually adjusted so that the device I!) will ignite andcause the alarm bell to ring or other device to function when the chargeon the storage condenser C! has been raised by either 3 or 4 successivesteps (i. e., correctly timed dashes and spaces), according to thecondition initially chosen.

The device 8 ignites and causes the storage condenser to be dischargedif the length of the signal exceeds 4.5 seconds, and the device 9 inites to perform a similar function if the space between successivesignals exceeds 1.5 seconds.

From the foregoing description it will be appreciated that the selectorsystem of the present invention constitutes a considerable improvementover the systems previously employed.

Unreliable mechanical devices are not required and the necessity foremploying costly apparatus, such as a voltage regulator, sensitiverelays and associated temperature control ovens, which in 6 thepasthave'been-essential in systems bf the electronic type, isavoided.

The positive operation of the-various selector relays by the dischargecurrent of gas discharge devices results in virtualindependenceof'norlnal plate supply variations and greatly improvedrelay action due to almost instantaneous change of relay current fromzero to operatingvalues, the latter being large enough to operatereliably the simplest types of relays. i

In the present system the expensive stepping switch usually employed inprior art systeins 'is eliminated, and replaced by a conventionalcapacitor type'integrator which controls mar-mg ing of alarm bellsthrough a gas discharge device and its associated-relay. Thisintegrator-may be adjusted very simply to ignite the gas dischargedevice on receipt of any predetermined number of signals. e c

1 What is claimed r l. Improvements in automatic alarm selectorarrangements, comprising, in combination, a'signal relay responsive toincoming signals, a first selector relay the operating winding ofwhichis energized by discharge current of a grid controlled gasdischarge device, circuit means in cluding a time constant network forapplying control potentials to the grid of said device a pre determinedtime after the operation of said signal relay, a storage circuit foraccumulating a potential increasing with successive operations of saidfirst selector relay, an alarm or indicating device, means responsive topotentials of a predetermined value in said storage circuit foractuating said alarm or indicating device; a second selector relay whichfunctions to discharge said storage circuit when the operating windingof said second selector relay is energized by the discharge current of asecond grid controlled gas discharge device, circuit means including atime constant network for applying control potentials to the grid ofsaid second discharge device when said first selector relay has beenoperated for a predetermined time; and a third selector relay theoperating winding of which is energized by the discharge current of athird grid controlled gas discharge device to discharge said storagecircuit a predetermined time after the opening of said first selectorrelay, the said selector arrangement including circuit means responsiveto incoming signals to render the said gas discharge devicesnon-conductive.

2. Improvements in automatic alarm selector arrangements, comprising, incombination, a signal relay responsive to amplified received radiosignals, a first selector relay arranged to be energized by thedischarge current of a grid controlled gas discharge device, circuitmeans including a time constant network for applying control potentialsto the grid of said gas discharge device a predetermined time afteroperation of said signal relay, a condenser for accumulating a potentialincreasing with successive operations of said first selector relay, analarm hell or bells or other appropriate indicating device, meansresponsive to potentials of a predetermined value attained across saidcondenser for actuating said bell or bells or other indicating device; asecond selector relay arranged to discharge said condenser when saidsecond selector relay is energized by discharge of a second gridcontrolled discharge device, a time constant network through the mediumof which control po- 76 tentials are applied to the grid of said seconddischarge device when said first selector relay has been operated for apredetermined time; and a third selector relay arranged to be energizedby the discharge current of a third grid controlled gas discharge deviceintended to discharge said condenser a predetermined time after openingof said first selector relay, the said selector arrangement includingcircuit means responsive to incoming signals to render the said gasdischarge devices non-conductive.

3. Improvements in automatic alarm selector arrangements, comprising, incombination, a signal relay responsive to amplified received radiosignals, a first gas discharge device with an associated relay arrangedto be energized a predetermined time after operation of said signalrelay to apply successive charges to a storage condenser, a gasdischarge device operatively associated with an alarm actuating relayand arranged to be fired by said storage condenser when successivecharges applied to the latter have reached a predetermined value, afurther gas discharge device with operatively associated relay arrangedto discharge said condenser if the length of a received signal exceeds apredetermined length of time and a still further gas discharge devicewith an operatively associated relay arranged to discharge saidcondenser if the space between successive received signals exceeds apredetermined length of time, the said selector arrangement includingcircuit means responsive to incoming signals to render the said gasdischarge devices non-conductive.

4. Improvements in automatic alarm selector arrangements, comprising acombination in accordance with claim 1. in which said means re- 8sponsive to potentials of a predetermined value of said storage circuitfor actuating said alarm or indicating device, consist in a gasdischarge device which is so biased that it will be fired whensuccessive charges applied to said storage circuit have attained apredetermined value.

5. Improvements in automatic alarm selector arrangements comprising acombination as claimed in claim 1, in which said means responsive topotentials of a predetermined value in said storage circuit foractuating said alarm or indicating device, consist of a gas dischargedevice which is variably biased so that it will be fired when apredetermined number of successive charges have been applied to saidstorage circuit.

6. Improvements in automatic alarm selector arrangements, comprising acombination in accordance with claim 1, in which positive biasingpotentials are applied to the cathodes said grid controlled gasdischarge devices.

FREDERICK SYDNEY HOLLOWAY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,094,733 Byrnes Oct. 5, 19372,110,015 Fitzgerald Mar. 1, 1938 2,235,804 Macalpine Mar. 18, 19412,441,145 Hansen May 11, 1948 2,442,702 Marrison June 1, 1948 FOREIGNPATENTS Number Country Date 437,539 Great Britain Oct. 31, 1935

